Breakthroughs in telecommunication technology in recent years has led to greatly improved telecommunication infrastructures. In particular, the advent of satellite communication networks has greatly improved global communication capabilities. Point-to-point, or "bent pipe" satellite communication systems, such as the one described in U.S. Pat. No. 4,720,873 to Goodman et al., provide fast economical communication service and improve the range of communication links over conventional land line communication systems by allowing the path of the communication link to be anywhere within view of (i.e., within the "footprint" of) the satellite. Satellite cellular telephone communication systems, such as the one shown in U.S. Pat. No. 5,410,728 to Bertiger et al., and commercially known as the IRIDIUM.TM. satellite communications system developed by Motorola, Inc. in Chandler, Ariz., improve over bent pipe satellite communication systems by providing global coverage and inter-satellite communication link capabilities. Thus, a subscriber unit of this system may communicate with any other subscriber unit or entity coupled to a public switched telephone network (PSTN) on or near the surface of the Earth. In each of the satellite communication systems just described or currently available, however, the location of both ends of the communication link (i.e., the calling party or caller and called party or callee) must be known in order to establish and maintain the communication link.
There are many applications, however, in which it would be desirable to establish a communication link and yet the location of the callee is unknown. The location of a callee may be unknown, for example, when the callee is in an unserviced or remote area (if global coverage is not provided), or where the callee is lost or incapable of reporting its location.
In addition, there are many occasions where the callee knows its location but it is undesirable for it to transmit its location. An example situation may be where it is desired to recover a lost person or device, and yet it would imperil the lost person or device to reveal the location.
There are also numerous applications in which it would be desirable to communicate via means other than voice. Examples of such situations include where it is desired to collect and or send data or control signals to a remote unmanned location or device, or when no response is received after attempting to communicate via voice.
Finally, there are many applications where portability and or mobility is desired. This may be useful, for example, in tracking changing conditions encountered by a remote moving entity.
Accordingly, a need exists for a method and apparatus for providing autonomous voice and or data communication, especially one for providing precise positional location self-determination capability without externally revealing the location, and for allowing remote sensor information to be collected and or acted upon, and for controlling an external device or equipment.